Uric acid is the final product of purine metabolism in the liver. The main route of uric acid excretion is the kidney. Approximately two-thirds of uric acid is excreted in the urine and the remaining is excreted in feces. Although blood uric acid is maintained inappropriate levels in healthy individuals, hyperuricemia is induced when an excessive production of uric acid or a decreased excretion of uric acid occurs.
Hyperuricemia, in which blood uric acid levels become elevated, is a factor that causes gout and urinary calculus, and furthermore it is said to contribute to nephropathy and arteriosclerosis. In addition, there have recently been an increasing number of reports that the higher the blood uric acid level, the higher the incidence rates of lifestyle-related diseases such as metabolic syndrome and hypertension, chronic kidney disease, and the like, and hyperuricemia is being recognized to be a risk factor for these diseases. Thus, an improvement in hyperuricemia is expected to lead to improvements in various diseases (Non-Patent Document 1).
Recently, the gene (SLC22A12) encoding a human renal urate transporter has been identified. The transporter (urate transporter 1, URAT1) encoded by this gene is a 12-transmembrane type molecule belonging to the OAT family. Its mRNA is specifically expressed in the kidney, and further, its localization on apical side of the proximal tubule has been observed in human kidney tissue sections. URAT1-mediated uric acid uptake has been shown by experiments using the Xenopus oocyte expression system. Furthermore, it has been reported that probenecid or benzbromarone, which inhibits URAT1, is useful agent for prevention or treatment of hyperuricemia, gout, and the like (Non-Patent Document 2).